With the development of mobile communication and the diversification of services, increasingly higher requirements are put forward on the transmission rate of communication systems. Carrier aggregation (CA) technology has been introduced into 3GPP Release 10 and Release 11, and is used to increase the downlink and uplink speeds of a system. That is, a user equipment (UE) can be configured with multiple carriers at the same time, and can simultaneously perform transmission and reception on these multiple carriers, which, compared with prior single-carrier transmission, greatly increases transmission speed and resource utilization rate.
In 3GPP Release 10 and Release 11, a serving base station (eNB) configures multiple carriers for the user equipment, and these carriers belong to the same base station. A cell which corresponds to the primary component carrier (PCC) of the serving base station is called a primary cell (PCell), and the primary component carrier provides radio resource control connection between the UE and the eNB and a transmission resource. A cell which corresponds to the secondary component carrier (SCC) of the serving base station is called a secondary cell (SCell), and the secondary cell is mainly used to provide a transmission resource. A PCell and one or more SCells are included in serving cells corresponding to the multiple carriers configured for the UE. In the R10/11 version of protocol, the UE can, at most, support eight serving cells at the same time.
In the R10/11 version of CA, only the configuration of physical uplink control channels (PUCCH) on the PCells is supported. That is, for a UE, configured SCells thereof do not have PUCCHs. Uplink control information (UCI) which is needed to optimize downlink transmission, such as a channel quality indicator, and hybrid automatic repeat request feedback (HARQ), needs to be transmitted via a PUCCH. In this case, the UCI corresponding to all the SCells needs to be carried by the PUCCH of the PCell.
The dual connectivity (DC) technology is introduced into 3GPP Release 12 to increase user throughput and improve mobility performance. When DC is configured, the UE can simultaneously communicate with two eNBs, each base station can maintain cell configuration similar to R10/R11 CA, and are divided into a master base station (Master eNB) and a secondary base station (Secondary eNB). In this case, for a UE, the MeNB can include a PCell and one or more SCell; and the SeNB can include a primary secondary cell (PSCell) and one or more SCells. PUCCHs can be configured on the PCell and the PSCell. Just as in CA, UCI of the PCell and SCells included in all the serving cells belonging to the MeNB is carried on the PUCCH of the PCell, and UCI of the PSCell and SCells included in all the serving cells belonging to the SeNB is carried on the PUCCH of the PSCell.
In ongoing Release 13, the enhanced CA technology (eCA) is being discussed. In eCA, PUCCHs on SCells are introduced, and moreover, the number of carriers capable of being simultaneously supported by a UE is increased to 32, so that the system resource utilization rate can be increased. However, adopting the PUCCH of a PCell or an SCell to carry the UCI of an SCell and adopting the PUCCH of which SCell to carry the UCI under SCell PUCCH configuration is an urgent problem that needs to be solved.